Rochester 2bbl motor recommendations.

[1DirtRacer1]

No ci rule, any cast iron straight plug head, rochester 1 1/4" venturi carb with matching intake. What would you motor guru's build ?

[Krooser]

Give us more to work with…. golf cart? 18 wheeler? Somewhere in between?

[LITE-INN]

its a 18 wheeled golf cart

[Brian Gray]

Big stroke small bore. In my opinion. The stroke will help get some low end power out of it but pay attention to your VE . This ensure the thing will keep pulling through the rpm range.

Compression is overrated especially with this scenario and if you hit the cam selection right you will end up with an engine that last many laps and make decent power. Keep it around 12:1 with as light a rotating assembly you can afford. Then consider dlc or cool blue coated parts. Friction is gonna be the real enemy to combat in this.

[stockcar5]

Compression is overrated especially with this scenario

You couldn't be more wrong.

[Brian Gray]

Please enlighten .

[50j]

Larger bore, smaller stroke, compression, play with rocker ratio.

[Krooser]

What's erratic about having compression? It's free HP… especially on LITE-INN'S 18 wheeled golf cart.

[Brian Gray]

Compression isn't free HP. In comes at a cost. It requires energy to compress the air fuel mixture. That requirement is multiplied as the ratio increases. It also comes at a premium because of the high cost of fuel needed for the engine to live under the scenario. Not to mention wear and tear on components and not just rotating assembly but all components. Compression stresses every part of the engine every part.

I believe the erratic part he's talking about are the sharp power spikes associated with high compression engines . these must be controlled with ignition timing and cam selection. The many classes that choose the 2 bbl small cfm carbs are mostly economy classes where torque is key to pulling heavy cars off the corners. I suggest the larger stroke to help this so there isn't a huge need to run the high rpm needed to get the same result from nascar style big bore short stroke engines.

How ever you decide weigh all of the options . Pay attention to the cubic inch needed per cfm available and choose based on what you think will help your chances of winning. I always opt on the side of
Durability when it comes to building an engine.

[Brian Gray]

Just remember this. All engines are air compressors. They pump and compress air. It requires energy to do that work. If you want to make more usable power in limited situations you have to focus on efficiency !

[perfconn]

If compression wasn't important then why were the Cup engines running 22 to 1 compression in their restricter plate engines until Nascar made them cut back to 12 to 1????

[1DirtRacer1]

So whats your thoughts on this subject Perfconn ? No C.I rule , no compression rule , no cam or valve train rules , they are just trying to control engine with carb rule. it's gotta be wet sump , steel block ,straight plug steel heads and rochester 2bbl steel intake 1 1/4" rochester 2 bbl carb, run on race gas.

[Brian Gray]

I said in this scenario compression is over rated. We were testing high compression to see how far you could go. Key word testing. How many cup engines do you think made the 500 mile trek around any track at 20:1 ? Cause I know. And telling a limited guy to go all out on high compression is absolutely retarded . you don't have the ability to fuel the motor beyond the limits of internal drag to build usable power.

[cheaterleaddog]

406 with 14.5 to 1 pistons machine domes to fit in 50cc heads. Don't know what final compression was but worked great. Had it so close that the valve would leave a imprint on carbon on top of piston. Mad fast and lasted for ever. After you turn more rpm's than carb will flow pressure in chamber starts dropping because less air/fuel gets into chamber this is where the reliability comes from. put a big carb on it and pack it full and head gaskets will be gone.

[perfconn]

1DirtRacer1,
I would build a big bore short stroke 360 or so ci with all the compression I could make.All the 2 barrel engines I have built were 15-1 with flattops.I used the Dart Iron Eagles(which you can't) and angle milled them to 36cc.Several factors make a good restricter plate(2 barrel) engine.All the compression you can make,as long a rod as you can fit in and a lot of rocker ratio.These are things that are proven to work in restricted engines but rules makers usually prevent you from doing them.